I know that whenever there are security updates (or other recommended updates), an orange logo would appear on the toolbar to remind me of updating. And then what I have to do is to click the logo and then enter my password and click "install update".

However, can this be performed through command line? My problem is that my computer is located in a place where I can only access remotely through SSH. I would still like to perform update through SSH. What should I do?

This is really distro dependent. Could you let us know what distro you are using?

For instance, debian based, (Ubuntu, Debian, etc) you would be able to run:
sudo apt-get update
sudo apt-get upgrade

sudo runs the command as root (updates must be run as root)
the update checks the repositories for updates to the package list
the upgrade does the upgrade of the packages.

Other distros use other commands... so let us know the distro you run, and we can probably help some more (and you can put this info in your profile so it appears just under your name in posts... so you dont have to tell us every time :-))

@BugZRevengE: This was posted in the Ubuntu forum, so lawrence_lee_lee is most likely talking about Ubuntu or a derivative

I thought it would be ubuntu, but I use kubuntu, and don't remember the colour of the icon, but figured it was going to be ubuntu orange :-) - I think kubuntu is a red exclamation mark or cross?

But without knowing, it is best to be sure of the distro.

If it is Ubuntu or derivate, security updates can be done automatically. It is a configuration option in the package manager/update manager.

Thanks everyone!

Yeah! You're right. I should have explicitly told my distro. I am using Ubuntu7.10. I am very interested in that apt-get command. I've "man" it but it seems so long and difficult to understand. Can anyone give a brief introduction on the command?

I am also very interested in how to make the update automatic. Thanks very much!

Automatic updates via GUI:

System --> Administration --> Software Sources: Checkbox: install security updates without confirmation

For apt check:
http://www.debian.org/doc/manuals/re...ackage.en.html

Note that, as the site points out, aptitude is now preferred over apt. It is a bit smarter at resolving dependencies.

kubuntu is ubuntu but basically with kubuntu components, etc.. instead of gnome :P